Radio reception system



-Aug.24-,1926. v 1,597,431

' w. B. BURGESS RADIO RECEPTION SYSTEM Filed May 14, 192} 2 Sheets-Sheet 1 1. 5 v l'l l l l e 25 gnuzhto'c I Warrn B. Burgess I dbtoznigq Aug. 24 1926; I 1 w. B. BURGESS RADIO RECEPT-ION SYSTEM Y Filed May 14, 1925 I 2 Sheets-Sheet 2 I glwue'nto'c Warren B. Burgess Patented Aug. 24 1926.

I I 1,597,431,: PATENT" OFFICE.

WARREN B. BURGESS, or 'wasnmeron, nrsrnror or COLUMBIA.

RADIO RECEPTION SYSTEM,

Application filed May 14, 1923. Serial No. 638,971.. 1

. My invention relates broadly. to radio reception systems, and more particularly to a? circuit arrangement for reducing the effects of body capacity upon the circuits of a 5 radio compass receiving-apparatus One of the objects of my i provide means to be connected to any standard vradio receiving apparatus for eliminating the capacity effect of the operators body-which normally forms with the circuits of the receiving apparatus. a portion of a radlo'frequency circuit.

Another object of the invention is to pro;

vide a system of radio'frequency choke '15 coilsarranged in the radio receiver circuits whereby radio frequency currents are sup pressed from leads extending any substantial distance from the receiving apparatus Another object of the invention is to provide one. or more radio frequency chokev coils having negligible impedance to audio frequency currents connected in the telephone circuit of the receiving apparatus whereby radio frequency currents aresuppressed from the telephone circuitand-no effect will be produced by movement of the operators v.body or the touching of any pa'rtooffthe receiving apparatus, andthe relative position of the operators body to the apparatus will have no influence upon the functioning of the radio receiving circuits.

My invention will be more clearly understood by reference to the following specification and the accompanying drawings, in which:

Figure 1. is aschematic wiring diagramof a radioreceivin'g apparatus used 1n connection with aradio compass showing my invention applied to the circuits thereof;

Fig. 2 is an elemental diagram illustrating a radio compass circuit withfswitches arranged for cutting in or removin gthe'v radio frequency choke coils from the telephone circuit Fig. 3's a theoretical characteristic curve show1ng the direction finder coil characteri stic and the advantages produced .therein fwhen employingmy invention in circuit withla radio compass receiving apparatus; Fig.4 is a perspective view of one form which the radio frequency choke coils of my invention may take Fig. 5 is a cross-sectional view taken on line 5-5' of Fig.4;

- Fig. 6 is a cross-sectional view taken on line 6-6 of Fig. 4; and

nvention' is to FigfT is a side elevation of one'of the radio frequency choke coils employed in my circuit arrangement;

In radio compass receiving systems great difficulty has been experienced in keeplnlg constant the capacity to ground of th'e'operators body while taking a hearing, The reason ,for this among other things is that the telephone 'leads capacitatively connect 0 the operatorsbody into a radio frequency circuit throughthe receiver, his body capacity shuntingthat of the batteries to ground. Normally changes in this capacity must be reproduced'in the compensating condenser in the compass circuit. to maintain the balance. In the past the only practical. means employed to obviate this difficulty has been to require-the operator to keep hisfeet on" .a stool away' from the-grounded screen, and hold his body-as still as possible when obtaining a balance. .Touchi g the 'metal spiderof the hand wheel for turning the compass or any other grounded metal, always destroyedthe balance when signals were loud enough to give good minima. 'In the present invention I- overcome this disadvantages by connecting radio frequency choke coils in one orboth'of the telephone leads immediately adjacent the amplifier and in the battery leads in, cases where they extend a substantial distance from the apparatus.- The radio frequency choke coils are constructed with low impedance to the audio frequency currents; in the telephone circuit, and leads may be run out of the station to aline system'for remote control from a distance without afl'ecting the compass balance or the stability of the amplifier.

In the usual radio compass installation the effect of movement of the operators body is to produce erroneous observations by. changing the minima signal intensity requiring a chanlge in the compensating capacity to make an accurate observation. Unless extreme caution is exercised by the operator .the observations may be a considerable per- 8 isused having collector. ring terminals 9- and 10 which connect with the receiving apparatus with timing condenser 12 shunted across the loop. The A-battery 14 and B- battery 15 may be located in some "installations at a substantial distance from the receiving apparatus and connected through extended leads with the filament heating cir- Y cuit 16 and-the plate circuit 17 of the receiver. Radio frequency choke coils 18,19 and 20 are interposed in the several leads immediately adjacent the receiver for suppressing' radio frequency currents from the leads extending to the batteries. There is an inherent capacity existing across each. of the radio frequency choks coils due. to the distributed capacity of the windings, and as thiscapacity tends to pass radio frequency currents around the'chokes, I provide for a construction to reduce this distributed capacity to a minimum. If a condenser is shunted around the chokesof such capacity value when combined with the inductance of the choke to form a local'circuit in resonance with radio frequency of the signal,

this tuned circuit will most\ effectively stop the passage of the radio frequency. This connected in shunt with choke 20. In the is illustrated in Fig. 1 as condenser 2O telephone circuit immediatelyadjacent the output circuit of the electron tube 6 I provide radio frequency choke coils 21 and 22.

The suppression of-radio frequencies from the. telephone circuit permits the circuit to be extended through conductors 2t, transformer or large inductance 25, switch 26,-'

- and-line wire system 27which may lead to aremote control radio compass station and deliver the telephone current. at such'point' without. deleterious capacity effects. telephones 28 which are worn by the operator when taking observations upon incoming signals are isolated from radio frequencies, and as the operator moves to different points'adjacent the apparatus no deleteriousg unbalancing is involved. Normally there, is the inherent-body capacity 29 to ground and capacity ofthe other parts of the circuit rep-resented at 30. These inher- -ent capacities normally integrate .to a capacity equivalent to that represented at 31, and

. while one particularvalue may be compensated. by varying'condenser 32 giving the normal characteristic curve to the radio compass represented at 33 in Fig. 3, variation in the capacities 29 and 30 by movement of the operators body is equivalent to variat on of capacity 31, thereby changing the ci aracteristic of the circuit to a curve as.

represented at 34, resulting in an uncertain m nimum s gnal readmg, or failure to show The a true minima. The provision of the radio frequency choke coils in my invention ob-- viates this disadvantage as heretofore pointed out. w c

Fig, 2 illustrates in an elemental manner the operation of my radio frequency choke coils. In this diagram adetector tube v4 is illustrated in connection with 1aradio .compass circuit having parts similarly operation of the radio compass with 'the switches 21 and 22 closed the compensating condenser 32 is adjusted for the best minimum, thereby balancing the antenna effect,

any inherent reradiat-ion, any unsymmetrical ground conditions, or other factors tending to obscure the null point. If now the capacity to ground through-the operators body changes, or other capacities to ground change, the null point will be obscured, as

illustrated by the characteristic 34 in Fig. 3,and a new balance will have to be struck by adjustment of .the compensating condenser 32. If the radio frequency choke lcoils 21 and. 22 are put into circuit by opening switches 21 and 22 the inherent capaity 29 is, in effect, cut off from the radio frequency circuit and capacity changes have no effect on the balance. The chokes are maintained-permanently in the circuit, their impedance'to the audio frequency telephone currents being small. The radio frequency choke coils may be embodied in structions.

The form illustrated in Fig. 4 comprises a case37 containing a pair of clockwise 'Wound radio frequency chokecoils 21 and.

22 with their ends connected to terminals P and S forming the input terminals, and

.B -and forming the output terminals. The terminal posts are separated at a maxi-'- mum distance apart to keep the capacity between the input and output leads to an absolute minimum to' secure the best effect from the chokes. The choke coils are spaced from each, other by means of the Washer 38 secured in position by bolt 39 passing through bushing 40 and the side walls of the casing 37. Suitable positioning means may. be passed through apertures 41 and 42 to secure the radio frequency choke coils immediately adjacent the output leads from the last. stage of amplification.

' While I have disclosed a particular embodiment of the radio frequency choke coils it is to be understood that I am not limited to this particular construction and that changes may be made 'within the scope of various conthe a pended. claims without departing from t e spirit of my invention.

Having thus described. my invention, what I claim and desire to secure by Letters Patent of the United States is as follows:

1. In a radio frequency receiving a system, the combination of a coil and tuning condenser, a plurality of current paths connecting said coil to earth, one of the paths consisting of a'variable condenser and another of' the paths comprising said tuning condenser effectively in series with groun capacity extending from portions of the system, the value of the capacity to ground being responsive to extraneous disturbances and means for rendering said value independent of the disturbances comprising a radio frequency choke coil.

2. Ina receiving system, the combination.

with a closed circuitincluding inductance and tuning condenser of a plurality of current paths connecting said coil to earth, one of the paths consisting of a variable condenser and another of the aths comprising said tuning condenser e ectively in series with ground capacit extending from portions of the system, t e value of the capacity to ground being responsive to extraneous disturbances and means interposed between said tuning condenser and the capacity to ground for rendering the value independent of the disturbances.

- actance o 3. In a direction finder, thecombination of a rotatable loop having a capacity area, two current paths in arallel extending from said area to groun ,-one of the paths consisting of two condensers, one of which operates substantially independent of ground capacity efiect and the other, being subject to momentary changes in value due rendered independent. .of said disturbances.

4. In a radio frequency system, the combination with a closed circuit comprising an inductance and a tuning condenser, of two current paths in parallel each including said inductance as a capacity area and a common capacity to ground the value of .which is responsive to extraneous disturbances, one of said paths comprising in addition, said tuning condenser, whereby the reactance of the paths are unequal, means in operative relation to one of said paths for equalizing said reactances and means connected with said common capacity to ground, for rendering the latter independent of the disturbances whereby equality between reactancesis preserved.

5. In a radio frequency-receiving system,

the combination with a closed circuit com prising an inductance and a tuning condenser, of two current paths in parallel each including said inductance as a capacity area and a common capacity to groun the value of which is responsive to extraneous disturbances, one of said paths comprising in addition, said tuning condenser, whereb the reactance of the paths are unequal means in operative relation to one of said paths for equalizing said reactances and means connected in series with said common capacity to ground, for rendering the latter in ependent of the disturbances whereboy equality between reactancesi is preserve said means comprising a filter impassable to radio frequency. a 6. In a receiving'system, .aclosed circuit comprising an inductance coil, and a tuning condenser, said coil having a capacity area, two parallel current paths extending from said area. to ground, one of said paths including'the tuning condenserand a pluralfectively in series with certain of said capacities for substantially eliminating saidbody capacity eflects whereby balance is maintained.

WARREN B. BURGESS. 

